Method of rolling tubes



April 26, 1927.

J. ROEDER ET m.

METHOD OF ROLLING TUBES Filed Jan, 11, 1927 tion of the ro methods used in rolling tubes.

enemas Apr. 26,1927.

name; sra'ras meager earner ser es.

JULIUS ROEDER WILHELM WELLMANN, OF WITTEN, GERMANY.

MTHOD OF TUBES.

Application filed January 11, 1927*; Serial No. 160,483, and in Germeny'lanuary 7, 192 6.

. Our invention relates to rollin mills and ore specifically this invention relates to a method for rolling tubes by the so-called Swedish process in which the pierced round is passed through blooming and roughing mills over a mandrel for the purpose of rolling the round into a long hollow bloom. After the usual cutting up into separate pieces has been effected on the same these pieces are reheated and rolled out into finished tubes on the finishing rolls. 7 Among the objects of our invention may be mentionedreducing to a minimum the number of passes at the finishing rolls, increasing the production of finished tubes, reducing the wear of the plug and the rod and economizing the heat required during the process.

' In order to accomplish these objects, we have combined certain wellknown types of mills in .a novel combination which is illustrated in the accompanying drawing.

The drawing represents a. layout in ac cordance with the invention, comprising blooming, roughing and reducing mills, a saw, a furnace and a finishing mil].

According to the method used at the present time, the pierced round is worked on blooming, roughing and finishing rolls in such a way that in each of the rolls the bloom passes through a definite number of grooves or passes of decreasin not only the external diameter 0 the bloom diameter,

or tube being diminished, but the wall thickness also beln diacr'eased by. suitable selecp u 's. 4 In rolling on a Sdvdish rolling mill,"that is to say, in rolling over a plug and .rod, a A number of inconveniences are experienced.- Atthe blooming mill and the roughing-mill the greatest possible weights are rolled for of long peace is exceedmgl the purpose of attaining large production.

As a result the rolled bloom on the roughing mill obtains a considerable length.. Experience ha'sproved, however, that-a very long bloom does not' veil? r be' d h 1 'li ii .o pierce mt epu ro in 1111 an furth d r i nore the wea'rof tile plug n the ca se is greater the further the temperature of the bloom falls during the rolhn process.

. Since the mandrel rods are 'su jected to bending and of the wall thickness from ass to pass must not be too great, becausgw en the eis stresses the reduction of the grooves rolling.

. .wit

y great, and it ends are formed which make it diflicult to bring the blooms back smoothly towards the pierced end. a

Finally in the event of the passes being too severe the roll plugs are very apt to break. All' of these circumstances prevent the bloom from being rolled down at the roughing mill beyond a certain diameter or beyond a. certain wall thickness, so that the bloom at the roughing mill after the last pass still has a comparatively large diameter. Now if at the finishin rolls tubes of small diameter and very thinwalls are to sult, particularly in the case of thin-walled tubes, that the tube becomes cold during the For the most part the tube is not finished in one heat and must be put back into the re-heating furnace for repeated reheating, or it does not have the wall thick-- ncss intended. As a result large quantities of iron scale are formed. These scalings represent an appreciable loss of'iron. Other results ofa large number of passes on the finishin rolls are a considerable wearing of the p ug breaking of the plug and probable damage to the roll pass as well as excessive, wear of the mandrel rod.

The present invention removes these de-v fects by 'interposin'g between the roughing mill and the finishing mill, a reducing mill upon which the bloims coming from the uced intheir diameter roughing mill are re out substantial change of wall. thickness. No mandrel is employed in the reducing mill. The bloom t passed. through a substantially smaller groove at'thefinishing mill than an unre- 'duced bloom coming directly from the roughing mill, so that a lar e "number'of. passes is saved, as-compared with the method hitherto employed.

A's statedabove there is alimit to the j to the loss of heat of the and the-(hi1 cult es arising through loss during rollrolling process in the r0 hing-mill i g us reduced. can, be

ing, that is to say it is impossible to proceed rolling the bloom in the Swedish rolling- .mill after the bloom has suffered a definite loss of heat, without reheating it. .Thevdisay, by causing said bloom to travel through a few passes of the latter only. The heat retained by the bloom after it has travelled through the last 'pass will be still sufficient to permit the reduction of its outer or inner di-' aineter respectively without using a mandrel, wherebv the thickness of the wall of the tube will be increased insignificantly. By reducing-mill a continuously working rolling-mill is to be understood, consisting of a certain number of pairs of rollers arranged one pair behind the other. The bloom coming from the roughing-mill is passed by means of conveying rollers to the reducing mill and passes the rollers of this apparatus, where it is reduced to 'a diameter, that will permit the bloom--after it has been divided into several arts-.to be rolled now o a tube of small thin wall, by causing the bloom to travel through a few passes of said apparatus only. Thus in contradistinction -to' the hitherto customary method, a considerable amount of work has been transferred from the finishing-mill to the reducing-mill. In connection with this it must be pointed out thatthe work in the reducing-mill is done with- .out manual labor, and that while the reducing-mill isrelieving' the operator from a ortion of his work, the operator will be ab e toroll a greater quantity of tubes, since with the-new arrangement he is able toemploy much less passes. v

Referring more particularly to the drawing, A is a blooming mill of known construction; B is, a roughing mill associated .therewith and H is the usual finishing mill.

Between theroughing mill B and the finishing mill Hare interposed a reducing mill D, a sa w F, 'and a reheating furnace G. A conveyor C facilitates the transfer of the bloom coming off of the roughing mill Bto iameter and very the reducing mill D. A second conveyor E leads from the reducing mill to the saw F. 4 The operation is as follows The ierced ingot, after being rolled out into a the roughing mill B passes over the conveyor C into the reducing mill D, and thence over the conveyor E to the saw F, where the subdivision of the bloom into separate lengths suitable for treatment in the finishing mill takes place.

loom in the blooming mill A and From the saw F, the separate 7 lengths go into the reheating furnace G,

and from there to the individual passes of the finishing mill H. They thus arrive at the finishing mill with a. considerably smaller diameter than they would have had, had they come directly'from-the roughing rolls according to the methods that have hitherto been used. They therefore need consid ably fewer passes for the purpose of rollin I them into a tube of small diameter and smal wall thickness.

In this way correspondingly less heat is wasted. No reheating bet-ween passe the finishing mill is required and a tube of very thin wall is finished while still warm. Greater reduction in diam'eter and in wall thickness can be'effected at each pass. For

these reasons wear of the plu and bending stresses in the rod are norma and mandrel breakages, together with resulting damage to the roll passes, ceases. Furthermore owing to the reduction of roll passes, at the finishing rolls, the production of finished tubes is increased very considerably.

We claim:-. a v A process for rolling tubes comprising passing the hollow body to be rolled, successively through a blooming mill over a mandrel, through a roughing mill over a man-' drel,-through a reducing mill, without omploying a mandrel, and through a finishing mill over a mandrel, the interposition of the reducing mill between the roughing mill and the finishing mill serving to reduce the number of. passes required at the finishing mill.

In'test-imony whereof we have signed our names to this specification.

JULIUS ROEDER. WILHELM WELLMANN. 

